Reticulopodia: Structural and behavioral basis for the suprageneric placement of Granuloreticulosan protists

A complex array of branching and anastomosing granular pseudopodia (reticulopodia) is thought to be a primary feature of the protistan phylum Granuloreticulosa. This essay summarizes the results of detailed structural and behavioral analyses of reticulopodia from representative species of naked, soft-shelled, and unilocular agglutinated Foraminifera. Promiscuous plasma membrane fusion, experimentally demonstrated here for the first time, together with the presence of tubulin polymorphs and a unique class of ellipsoid vesicles, form a suite of phenotypic characters that further define the suprageneric status of these protists. A theoretical framework for exploring the evolution of reticulopodia is also presented.